160 MEMBRANIPORID.^. 



one only is usually permanent, but occasionally a second 

 survives. When the ovicell is absent there is some 

 amount of irregularity in the number and position of the 

 avicularia ; sometimes the mandibles are turned down- 

 wards_, as is frequently the case amongst the Membrani- 

 porce under such circumstances ; sometimes only a single 

 avicularium is developed, which is placed crossways, or 

 in the centre, with its mandible pointing straight down- 

 wards. This very distinct form has probably been con- 

 founded with M. Flemingii, which, as I have pointed out 

 elsewhere, has had a character for inconstancy which it 

 by no means deserves. 



Membranifora imbellis, Hincks. 



Plate XX. figs. 1, 2. 



Membranifora imbellis, Hincks, Quart. Journ. Micr. Sc. viii. (1860), 275, 

 pi. XXX. fig. 1 ; Devon & Cornw. Oat., Ann. N. H. ser. 3, 

 ix. 28 (38 sep.) : Norman, Shetland Polyzoa, Rep. Brit. Ass. 

 1868, 305. 



Zooecia large, pyriform, contracted above and much ex- 

 panded below ; covering of the area wholly mem- 

 branous ; margin crenate or coarsely granulated, 

 thickened, especially at the bottom of the cell, where 

 it is usually somewhat produced and pointed. Ocecia 

 very prominent, frosted, with a depressed somewhat 

 quadrate area in front. No spines or avicularia. 



B/ANGE OF Variation. There is very great constancy in 

 the leading characters. The cells differ to some extent in 

 shape and size, and occasionally assume a subtriangular 

 form. 



Habitat. On shells, stones, &c., from deep water. 



Localities. Coast of Antrim (Hyndman) : Scotland, 



